The present invention relates to a pulse motor driving apparatus and, more particularly, to a driving apparatus for a pulse motor which is used in a copying machine.
In a copying machine of the fixed document table type, an optical section including an exposure lamp, mirrors, etc., is reciprocatingly moved along the fixed document table, and a document on the document table is optically scanned. When an image of the document is enlarged or reduced in such a copying machine, a lens block provided in the optical section is moved. A pulse motor is used to move this lens block. This pulse motor is driven by a two-phase excitation mode for exciting two phase windings at a time, since a strong torque is needed to move the lens block. However, in this two-phase excitation, when the excitation is cut off (i.e., when the pulse motor stops), the rotor is attracted to one of the two phases whose magnetic force is stronger than the other, and is stopped at the location of that phase. Thus, the stop position of the lens block to be driven by this rotor would have been shifted from the normal position, so that it would be impossible to obtain an accurate magnification, or reduction power.